CNT-Coated Battery Separator for Conductivity and Li-Ion Diffusion
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Solution Overview
Problem
Conventional methods for improving the conductive path of electrodes in lithium secondary batteries are insufficient, leading to suboptimal input/output characteristics and lithium ion diffusion in batteries.
Innovation Solution
A separator with a porous substrate and a conductive layer featuring carbon nanotube structures, where multiple single-walled carbon nanotube units are bonded side by side, enhancing the conductive path while maintaining lithium ion diffusion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods using current collector or conductive agent are used to improve electrode conductivity, then conductive path is improved, but input/output characteristics remain suboptimal
Solution Approach 1:
The patent changes the physical and chemical parameters of the separator by introducing a conductive layer containing carbon nanotubes and metal nanoparticles. This layer has specific conductivity values (10^-3 to 10^3 S/m) and thickness (1 to 1000 nm) that optimize both electrode conductivity and battery input/output characteristics, resolving the contradiction between conductive path improvement and overall performance enhancement.
Solution Approach 2:
The patent creates a composite structure by depositing a conductive layer on the separator surface. This layer combines carbon nanotubes (providing conductive network) with metal nanoparticles (enhancing conductivity and catalytic activity), forming a composite material that simultaneously improves conductive path and input/output characteristics beyond what conventional single-material approaches achieve.
2Reliability
If conductive layer is added to improve electrode conductivity, then conductive path is enhanced, but lithium ion diffusion may be hindered
Solution Approach 1:
The patent uses an ultrathin conductive layer (1 to 1000 nm thickness) as a flexible coating on the separator surface. This thin film provides sufficient conductivity enhancement while maintaining high lithium ion diffusion speed, as the minimal thickness ensures ion transport pathways remain open and unobstructed, resolving the contradiction between conductivity improvement and ion diffusion maintenance.
Solution Approach 2:
The conductive layer is designed with porous structure containing carbon nanotubes and metal nanoparticles distributed within the pores. This porous architecture provides continuous conductive pathways for electrons while simultaneously maintaining open channels for lithium ion diffusion, allowing both functions to operate efficiently without mutual interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves battery resistance and input/output characteristics by forming a robust conductive network that reduces battery resistance and maintains lithium ion diffusion, thereby enhancing battery performance.
Implementation Method 1
a conductive layer disposed on the porous substrate, wherein the conductive layer includes carbon nanotube structures
Implementation Method 2
maintaining a degree of diffusion of lithium ions of the separator
Data Source
AI summary
Provided is a separator including a porous substrate and a conductive layer disposed on the porous substrate, wherein the conductive layer includes a carbon nanotube structure including a plurality of single-walled carbon nanotube units bonded to each other side by side, and the carbon nanotube structure has an average diameter of 2 nm to 500 nm. Further provided is a secondary battery including the same.